Role of Iron(III)-salen Chloride as Oxidizing Agent with Thiodiglycolic Acid: The Effect of Axial Ligands

Abstract

The sulfoxidation of thiodiglycolic acid with iron(III)-salen chloride, which acts as an oxidizing agent without any terminal oxidant, in 50% aqueous acetonitrile medium has been studied. A substantial red shift in the λ<sub>max</sub>value of FeIII-salen was observed in aqueous medium. The spectrophotometric kinetic study indicates that [Fe<sup>III</sup>(salen)]+ is the active oxidizing species and the reaction follows Michaelis-Menten kinetics with respect to the substrate. The rate of the reaction is highly sensitive to the medium. A reaction mechanism involving electron transfer from sulfur atom of thiodiglycolic acid to the central iron atom of [Fe<sup>III</sup>(salen)]<sup>+</sup> is proposed. The presence of nitrogenous bases like pyridine, imidazole and 1-methylimidazole shows a retarding effect on the reaction rate. This can be explained on the basis of binding of these ligands to the coordination sphere of [Fe<sup>III</sup>(salen)]<sup>+</sup> prior to the reaction with the substrate. The observed order of reactivity, pyridine > 1-methylimidazole > imidazole, is in accordance with the inverse of <em>π</em>-donating ability of nitrogen bases.

A kinetic study and mechanisms of reduction of N, N′-phenylenebis(salicyalideneiminato)cobalt(III) by L-ascorbic acid in DMSO-water medium

“…The molar conductivity of [Co(Salophen)]Cl in H 2 O: DMSO is reliable to 1:1 electrolytic ratio. The occurrence of [Fe(Salphen)] + in DMSO-H 2 O (ratio 1:4 v/v), [Fe (salen)] + species in DMSO–H 2 O (ratio 4:1 v/v), CH 3 CN–H 2 O in (ratio 1:1 v/v) and [Co(Salophen).H 2 O] in (H 2 O) solvent systems have been reported previously ( Ibrahim et al., 2019a ; Liou and Wang, 2000 ; Pizzolato et al., 2013 ; Subramaniam et al., 2014 ).…”

“…So far, various kinetics and mechanisms of Salophen complexes of iron ( Ibrahim et al., 2019a , 2019b ; Subramaniam et al., 2014 ), cobalt ( Abdulsalam et al., 2020 ) and manganese ( Jena et al., 2018 ) have been recently reported. Herein, we report on the kinetic study and mechanisms of reduction of N, N′ -phenylene bis (salicyalideneiminato)cobalt (III) complex ([Co(Salophen)] + ) by H 2 A in a mixed aqueous medium.…”